Presently, an electrophotographic liquid developer is prepared by finely dispersing a dye or pigment such as Nigrosine, carbon black, etc., in a high-insulating liquid using an alkyd resin. The dispersing is carried out by a known dispersing means such as a ball mill. However, such a liquid developer is liable to cause aggregation or sedimentation with the passage of time. Therefore, difficulties occur in connection with the use of such developers. Other methods have been proposed such as a method of dispersing a pigment or dye using a synthetic polymer composed of a long chain methacrylate or acrylate as the main component and a method of stabilizing a dispersion of toner particles by grafting a polymer to the surface of carbon black. However, the images obtained by such a liquid developer have less resin component at the image portions and the fixing property of the images is not always sufficient. Moreover, when such a liquid developer is used for making a printing plate by utilizing electrophotography, there are difficulties because the sensitivity to the printing ink is insufficient.
In order to overcome these difficulties, a liquid developer has been proposed which is composed of a mixture of an ordinary liquid developer of a dispersion of a pigment or dye, and resin particles, as disclosed in Japanese Patent Application (OPI) No. 54029/79 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application") corresponding to U.S. Pat. No. 3,990,980. The liquid developer composed of the dispersion of pigment particles and resin particles attaches a comparatively large amount of resin components to developed image portions. Accordingly, the image portions are excellent in fixing property and when the liquid developer is used as a developer for making printing plate by utilizing electrophotography, the image portions have good sensitivity for printing ink. However, the liquid developer in which pigment particles and resin particles are simultaneously dispersed is not desirable because the charging characteristics of the resin particles are insufficient as compared to those of the pigment components.